Rational design of interfacial bonds within dual carbon-protected manganese oxide towards durable aqueous zinc ion battery

Manganese-based cathode materials are promising candidates for aqueous zinc ion batteries (AZIBs) by reason of their low cost and high energy density. However, their practical applicability is hampered by the intrinsic defects of poor electrical conductivity, sluggish reaction kinetics, and severe structural deterioration. Herein, we constructed a hierarchically porous structure composed of carbon-encapsulated MnO nanoparticles (MOC) and three-dimensional (3D) nitrogen-doped graphene aerogel (NGA) (denoted as MOC@NGA). The hybrid was synthesized by a facile in-situ coprecipitation and annealing of manganese-based metal-organic framework (Mn-MOF74) and NGA composite (Mn-MOF74@NGA). Specifically, the carbon shells inherited from organic ligand of Mn-MOF74 could restrain the volume changes of MnO, and the porous NGA prevented the agglomeration of MOC nanoparticles and enriched the types of interfacial chemical bonds. Profiting from the synergistic effect of rich interface chemical bonds and dual-carbon protection, the MOC@NGA hybrids exhibit fast interfacial electron/charge transfer and transport, and outstanding structural stability. Therefore, MOC@NGA cathode delivers an excellent rate performance (270 and 99.8 mAh g (-1) at 0.1 and 2.0 A g(-1)) and maintains an excellent specific capacity of 151.6 mAh g (-1) after 2,000 cycles at 1.0 A g(-1). Moreover, the fabricated MOC@NGA-based quasi-solid-state battery not only achieves outstanding flexibility but also displays impressive cycling stability, demonstrating a promising potential for portable and flexible equipment. This work provides a feasible strategy for the fabrication of the bridging structure of manganese-based oxides and porous carbon matrix for high-specific capacity and durable AZIBs cathodes.

Automated summary

In this study, a hierarchically porous structure composed of carbon-encapsulated MnO nanoparticles and nitrogen-doped graphene aerogel was constructed. The synthesized MOC@NGA composite exhibited fast interfacial electron/charge transfer, outstanding structural stability, excellent rate performance, and cycling stability, making it a promising candidate for AZIBs cathodes.